1. Field of the Invention
Generally, the field of the present invention is optical fiber management. More particularly, the present invention relates to a fiber monitoring apparatus and system for detecting the occurrence of a thermal event, especially of a traumatic nature, in an optical fiber while transmitting a laser beam.
2. Background Art
Optical fibers are widely employed in transmitting laser beams from lasers to end uses in diverse applications. An optical fiber is typically composed of a central core surrounded by a concentric cladding. Ideally, during its transmission a laser beam is completely contained in the central core by total internal reflection due to slight differences in the indices of refraction of the material of the core and cladding. Typical material, such as fused silica, used to form the core and cladding is susceptible to developing defects, particularly cracks or fractures, shortening the useful life of the optical fiber. At times these defects may evolve into a failure of the optical fiber that can have deleterious consequences.
One such consequence is where an optical fiber failure is sufficient to provoke the occurrence of a thermal event, especially of a traumatic nature, in an optical fiber transmitting a high power laser beam, having the potential to create a fire hazard, because the laser continues to operate. The optical fiber could burn back towards the laser like a fuse at very high temperature and ignite flammable components in the vicinity of the burning fiber. If the fiber is left to burn back to the laser, the laser might also be damaged.
The potential hazard of optical fiber failure has been generally recognized for many years, and various approaches to finding solutions to this problem have been proposed. One approach is to provide an optical fiber with a breakage sensor which takes the form of a fragile wire that is embedded within the jacket of the fiber such that when an event (whether thermal or mechanical) occurs that breaks the wire, a circuit opens and an interlock may be triggered to shut off the laser. A similar approach disclosed in U.S. Pat. No. 5,012,087, which issued in 1991 to Rockstroh et al., proposes to place a second optical fiber together with the laser power transmitting fiber in a jacketing tube or conduit encompassing both such that laser energy leaking from a damaged portion of the laser power transmitting fiber will cause failure of the second optical fiber which in turn would operate to shut off power to the laser before the jacketing conduit is adversely affected. However, both these approaches are deficient in that they would likely require significant added costs in order to initially provide each fiber with a companion failure sensing component of substantially the same length and then later have to provide replacement of both the damaged failure sensing component and the fiber.
Another approach disclosed in U.S. Pat. No. 4,476,512, which issued in 1984 to Sunago et al., proposes to position heat-sensitive elements near the input and output ends and the center of the optical fiber. These elements will produce signals that are processed by a detector circuit to indicate an abnormal increase or decrease in laser power at the center of the fiber for detecting a damaged fiber or abnormal laser light source. However, the disclosure of this approach is deficient in that no details are provided in this patent instructing what device or technique might be used to deploy the heat-sensitive elements relative to the fiber. Thus, further significant development efforts and innovative problem solving would likely be needed to determine the effectiveness of this approach.
Thus, in view of the deficiencies of the foregoing approaches, it is apparent that there still remains a long-felt pressing need for an innovation that provides an effective solution to the problem of an optical fiber failure potentially having deleterious consequences.